Server cooling system without the use of vapor compression refrigeration

ABSTRACT

A system, method, and computer product for cooling a server center without the use of vapor compression refrigeration. An example embodiment involves using outdoor ambient air to cool first server components directly and to cool heat exchanges containing liquid used to cool second server components.

BACKGROUND

This invention relates to data center cooling, and more particularly toa system and a method to increase cooling efficiency without the use ofvapor compression refrigeration.

The energy consumed by data centers has doubled over the past six yearand is predicted to keep increasing at the same rate. Up to fortypercent of the power consumed by data centers is used to cool them to anoptimum operating temperature. Current systems using vapor compressionrefrigeration require significant amounts of energy to operate.

Recent trends to reduce energy have resulted in systems using onlyliquid circulation to transfer the heat out of the server. These systemspump the liquid containing heat from the servers through outdoor heatexchangers that allow the heat to dissipate into the outdoor air. Thecool liquid is circulated back into to server where it is used to coolthe air circulating in the server and to directly cool servercomponents. However, these systems still require large amount of powerto operate the pump and fans.

BRIEF SUMMARY

Accordingly, one example aspect of the present invention is a system forcooling a data center. This system includes fans that form an aircooling path to cool a first set of server components and a pumpcirculating a liquid to cool a second set of server components. Thefirst set of components is cooled by convection to outdoor ambient air.This is accomplished by passing the outdoor ambient air over the firstset of server components. The second set of server components is cooledby direct thermal conduction into the liquid. The liquid is cooled byflowing outdoor ambient air over a heat exchanger containing the heatedliquid. This is all accomplished without the use of vapor compressionrefrigeration.

Another example of the present invention is a method for cooling a datacenter. The method includes forming an air cooling path to cool a firstset of server components and circulating a liquid to cool a second setof server components. The air cooling path passes outdoor ambient airover the first set of server components to cool them by convection. Thecirculating liquid cools the second set of server components by directthermal conduction into the liquid. The liquid is cooled without the useof vapor compression refrigeration, by flowing outdoor ambient air overa heat exchanger containing the heated liquid.

Yet a further example of the invention is a computer program product forcooling a server center. The computer program product includes computerreadable program code configured to form an air cooling path to cool afirst set of server components by convection to outdoor ambient air andto circulate a liquid to cool a second set of server components. The aircooling path uses convection to cool the first set of server componentsby passing outdoor ambient air over them. The circulated liquid coolsthe second set of server components through direct thermal conductioninto the liquid. The liquid is cooled by flowing outdoor ambient airover a heat exchanger containing the heated liquid with use of vaporcompression refrigeration.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other objects, features, andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 shows a cross-sectional view of an example of the server coolingcenter according to one embodiment of the present invention.

FIG. 2 shows a cross-sectional view of another embodiment of the presentinvention.

FIG. 3 shows a cross-sectional view of another embodiment of the presentinvention.

FIG. 4 shows an example cooling schematic for a server circuit board.

FIG. 5 shows a method for cooling server centers in accordance with oneembodiment of the present invention.

DETAILED DESCRIPTION

The present invention is described with reference to embodiments of theinvention. Throughout the description of the invention reference is madeto FIGS. 1-5. When referring to the figures, like structures andelements shown throughout are indicated with like reference numerals.

Embodiments of the present invention use an air cooling path and acirculating liquid for cooling a server center. The air cooling pathcools a first set of server components by convection to outdoor ambientair by passing the outdoor ambient air over the first server components.The circulating liquid cools a second set of server components throughdirect thermal conduction into the liquid. The liquid is cooled byflowing outdoor ambient air over a heat exchanger without the use of avapor compression refrigeration unit.

FIG. 1 shows a cross-sectional view of an embodiment of the servercooling center 102 according to the present invention. The servercooling center 102 includes multiple fans 104 and a pump 106. As usedherein, a “fan” is any device that can create airflow. A “pump” as usedin this application refers to any device that can generate liquid flow.The fans 104 form an air cooling path 108, 120 pulling outdoor ambientair into the server cooling center 102. The air cooling path 120 coolsthe first server components 110 by convention to air. The pump 106circulates a liquid coolant to cool second server components 112 throughdirect thermal conduction into the liquid coolant. This liquid coolantis cooled by flowing outdoor ambient air over a heat exchanger 114containing the liquid. The liquid coolant is cooled without the use ofvapor compression refrigeration.

This system will be most effective if the first server components 110are the components that produce less heat such as hard drives, powermodules, and other miscellaneous server products. The second servercomponents 112 should be components creating the most heat such as CPUsand memory modules.

The specific embodiment shown in FIG. 1 has multiple sidewalls 128. Eachsidewall has a first side exposed to the outdoor ambient air, and asecond side facing the first server components 110 and the second servercomponents 112. The sidewalls 128 have openings creating fluidcontinuity with the first and second side. This allows outdoor ambientair to enter the cooling center 102. Air filters and louvers can be usedto weather guard and control air flow through the openings. Multiplechimneys 116 allow the heated air 130 to flow out of the cooling center102.

An embodiment of the present invention may have a raised floor 118. Air120 entering below the raised floor 118 is channeled to the first servercomponents 110. Air 108 entering above the raised floor 118 is channeledto the heat exchangers 114 containing the liquid cooling the secondserver components 112. Air warming heat exchangers 122 containing theliquid used to cool the second server components 112 can be positionedbelow the raised floor 118 in the air cooling path 108 to heat cold airthat could cause condensation when heated in the server center.

The server racks 124 in the server cooling center holding the firstserver components 110 and second server components 112 can be perforatedto allow the air to flow over the first server components 110. Servershelves 126 may be positioned horizontal to the airflow path tofacilitate airflow.

One embodiment of the present invention can use valves 128 to controlflow of the liquid coolant circulating through the system. If theoutdoor ambient air is warm, the valves direct liquid coolant throughall the heat exchanges 114 to maximizing cooling. If the outdoor ambientair is cold, valves may direct the liquid coolant through a portion ofthe heat exchangers 114 necessary to cool the servers. The valves 128can also flow warm liquid coolant through the air heating heatexchangers 122 to warm the entering air.

One advantage of the configuration described above is that both the airloop and the liquid coolant loop have a shorter thermal resistance pathfrom the server to the outdoor ambient. Thus, the cooling system wouldbe highly efficient. The temperature of the air in the air cooling pathand the circulated liquid may be as low as the outdoor ambienttemperature or a couple degrees Celsius above the outdoor ambienttemperature.

Implementation of the inventive system described herein to an existingliquid cooled data center may require either the restructuring/replacingof some hardware components or use of new additional hardware componentsor both. Once the required hardware is installed, the controls in theproposed invention could be implemented in a number of ways. One way isto program the control schemes onto the PLC (programmable logiccontroller) unit of the data center facility. Another way is to run thecontrol algorithm on a remote computer/server which takes in therequired input information from the data center components and outputsthe optimum operational point.

FIG. 2 shows a cross-sectional view of a second embodiment of thepresent invention. According to this embodiment the outdoor ambient air202 would flow in through an entrance sidewall 204 and heated air 218would exit through an exit side wall 206. The airflow is produced byfans 208 inside the server racks 210. The server rack 212 in thisembodiment can have its front and rear surfaces perforated to facilitateairflow through the rack.

In this embodiment, a first heat exchanger 214 is placed next to theentrance sidewall 204 and a second heat exchanger 216 is placed next tothe exit sidewall 206. The server racks are positioned in between theheat exchangers 214, 216. In one embodiment, there are no fans next tothe heat exchangers. The fans in the server rack 210 thus create theairflow necessary to cool the heat exchangers.

Heated liquid exiting the server flows through the first heat exchanger214. If the liquid is required to be cooled further it is passed throughthe second heat exchanger 216. Valves are used to guide the liquidthrough the different heat exchangers as per needed. The heat exchangernext to the second wall is optional and can be used in cases where theair temperature leaving the server is lower than the liquid temperatureleaving the heat exchanger.

FIG. 3 shows a cross-sectional view of a third embodiment of the presentinvention. This embodiment is similar to the embodiment in FIG. 2, thedifference being that the airflow is produced by fans 302 outside of theserver rack 304 next to the heat exchanger 306. This allows for largerfans, having, for example, a diameter above 200 mm. Larger fans areadvantageous because they create airflow more efficiently.

FIG. 4 shows an example cooling schematic for a server circuit board402. The components 404 that generate high amount of heat are cooled byliquid coolant and the components 406 generating less heat are cooled byair with the use of heat sinks.

FIG. 5 shows a method 502 for cooling server centers in accordance withone embodiment of the present invention. The method includes an airintroduction step 504. During step 504 outdoor ambient air can be passedinto the entrance of the server center through opening in the sidewalls.Airflow into the server center can be controlled by the use of louversand air filters on the openings in the sidewalls. The louvers and airfilters can also weather guard the openings to prevent unwantedsubstances from entering the server center. After air introduction step504 is initiated, the method 502 continues to air channeling step 506.

At air channeling step 506, air entering the server center above araised floor is channeled to heat exchangers and air entering the servercenter below the raised floor is channeled to first server components.After air channeling step 506 is initiated, the method 502 continues toforming step 508.

At forming step 508, an air cooling path is formed to direct outdoorambient air to pass over first server components. The air cools theserver components by convection to the outdoor ambient air passed overthem. Heat sinks can be attached to the components to increase surfacearea in contact with the passing air. This will increase heat transferfrom the components to the air resulting in more effective cooling.Cooling components by convection to air is a more efficient process thanthermal conduction into a liquid. While more efficient, convection toair is less effective at removing heat from a component than directthermal conduction into a liquid. Therefore, the first server componentsshould be the components that generate the least amount of heat. Afterforming step 508 is initiated, the method 502 continues to liquidcirculation step 510.

At liquid circulation step 510, a circulated liquid may be used toextract heat from second server components through direct thermalconduction into the liquid. This process is more effective at removingheat that by convection to air. Therefore, it is advantageous for thesecond set of server components to be the components that generate themost heat. After liquid circulation step 510 is initiated, the method502 continues to step 512.

At liquid cooling step 512, the liquid heated by the second servercomponents can be cooled by flowing outdoor ambient air over a heatexchanger containing the liquid. Outdoor ambient air previously heatedby cooling other heat sinks or first server components may be used tocool the heat exchanges as long as it is colder than the liquid in theheat exchanger. After liquid cooling step 512 is initiated, the method502 continues to flow control step 514.

At flow control step 514, valves control flow of the liquid throughdifferent heat exchanger based on the amount of cooling necessary andthe temperature of the outdoor ambient air. If the outdoor ambient airis cold, the liquid coolant may only need to travel through a portion ofthe heat exchangers to dissipate the necessary amount of heat.Similarly, if the outdoor ambient air is hot the liquid coolant may haveto run through all the heat exchanger to dissipate the necessary amountof heat. Change in server workload may cause various amounts of heat tobe generated, resulting in more or less heat exchanges to be used. Afterflow step 514 is initiated, the method 502 continues to exhaustion step516.

At exhaustion step 516, the air heated by the first server componentsand the heat exchangers may leave the server center through a chimney inthe roof. In different embodiments the heated air may also leave throughsidewalls or ductwork.

Embodiment of the present invention can advantageously an ambient cooledsystem to operate at higher outdoor ambient temperature, eliminating theneed for any vapor-compression high energy refrigeration during theentire year. Liquid cooling is much more thermally efficient at removingheat components by direct thermal conduction than air cooling. However,it is not practical to have direct thermal conduction of all computercomponents so such systems are usually limited to high power densitycomponents such as processors and memory. Air cooling systems are easyto implement but do not provide the cooling capability of liquid cooledsystems.

Systems described herein can use the air ambient environment to bothprovide liquid and air cooling. Conventional systems that use ambienttypically use only liquid or air ambient but not both. Using the outdoorambient for both liquid and air cooling offers significant advantages inthe maximum operable outdoor ambient conditions and lower power usageeven when operating at high outdoor ambient temperatures.

This is achieved by both the air loop and the liquid coolant loop havinga shorter thermal resistance path from the servers to the outdoorambient. Thus, the cooling system is highly efficient. Moreover, the airtemperature as well as the liquid temperature seen by the servers can beas low as the outdoor ambient temperature or a couple of degrees Celsiusabove the outdoor ambient temperature.

This enables extending the server environmental from A2 (35 C) ASHRAEspecifications to A3 (40 C) and A4 (45 C) ASHRAE specifications. As thissystem allows for higher outdoor ambient temperature operations, thecooling power can be greatly reduced when the outdoor ambienttemperature is lower than the maximum design specification. Furthermore,this system enables the integration of free/ambient air cooling andfree/ambient liquid cooling of data centers.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A server cooling center comprising: a pluralityof fans forming an air cooling path to cool first server components byconvection to outdoor ambient air by passing the outdoor ambient airover the first server components. a pump circulating a liquid coolant tocool second server components through direct thermal conduction into theliquid coolant, the liquid coolant is cooled by flowing the outdoorambient air over a heat exchanger without the use of a vapor compressionrefrigeration unit.
 2. The cooling center of claim 1, furthercomprising: a plurality of sidewalls, each sidewall including a firstside exposed to the outdoor ambient air and second side facing firstserver components and second server components, the side walls havingopenings to allow the outdoor ambient air into the cooling center; andat least one chimney allowing heated air to flow out of the coolingcenter.
 3. The cooling center of claim 2, further comprising at leastone of air filters and louvers, configured to weather guard and controlair flow through the openings in the sidewalls.
 4. The cooling center ofclaim 2, further comprising a raised floor, the outdoor ambient airentering above the raised floor is channeled to the heat exchangers andthe outdoor ambient air entering below the raised floor is channeled tothe first server components.
 5. The cooling center of claim 4, furthercomprising a second heat exchanger positioned below the raised flooralong at least part of the air cooling path.
 6. The cooling center ofclaim 1, further comprising server racks with perforated surfacesallowing for airflow through the racks.
 7. The cooling center of claim1, wherein the heat exchanger are positioned at an entrance of the aircooling path.
 8. The cooling center of claim 1, further comprisingvalves to control flow of the liquid coolant through different heatexchangers.
 9. The cooling system of claim 1, wherein the plurality offans is proximate to the heat exchangers, the fans having a diametergreater than 200 mm.
 10. A method for cooling a server centercomprising: forming an air cooling path to cool first server componentsby convection to outdoor ambient air by passing the outdoor ambient airover the first server components. circulating a liquid coolant to coolsecond server components through direct thermal conduction into theliquid coolant, the liquid coolant is cooled by flowing the outdoorambient air over a heat exchanger without the use of a vapor compressionrefrigeration unit.
 11. The method of claim 10, further comprising:passing outdoor ambient air into the entrance of the server centerthrough openings on a plurality of sidewalls, each sidewall including afirst side exposed to the outdoor ambient air and second side facingfirst server components and second server components; and passing heatedair out of the cooling center through at least one chimney.
 12. Themethod of claim 11, further comprising controlling airflow through theopenings in the server center sidewalls using at least one of airfilters and louvers.
 13. The method of claim 11, further comprisingchanneling the outdoor ambient air entering above a raised floor to theheat exchangers and channeling the outdoor ambient air entering belowthe raised floor to the first server components.
 14. The method of claim10, further comprising controlling flow of the liquid through differentheat exchangers using valves.
 15. A computer program product for coolinga server center, the computer program product comprising: a computerreadable storage medium having computer readable program code embodiedtherewith, the computer readable program code configured to: form an aircooling path to cool first server components by convection to outdoorambient air by passing outdoor ambient air over the first servercomponents. circulate a liquid coolant to cool second server componentsthrough direct thermal conduction into the liquid coolant, the liquidcoolant is cooled by flowing the outdoor ambient air over a heatexchanger without the use of a vapor compression refrigeration unit. 16.The computer program product of claim 15, further comprising computerreadable code configured to: pass outdoor ambient air into the entranceof the server center through openings on a plurality of sidewalls, eachsidewall includes a first side exposed to the outdoor ambient air andsecond side facing first server components and second server components;and pass heated air out of the cooling center through at least onechimney.
 17. The computer program product of claim 16, furthercomprising computer readable program code to control airflow throughopenings in the server center sidewalls using at least one of filtersand louvers.
 18. The computer program product of claim 16, furthercomprising computer readable program code to channel the outdoor ambientair entering above a raised floor to the heat exchangers and channel theoutdoor ambient air entering below the raised floor to the first servercomponents.
 19. The computer program product of claim 15, furthercomprising computer readable program code to control flow of the liquidcoolant through different heat exchangers using valves.